The invention relates to an improved method of producing binary self condensation products of phenols. The products formed are substituted biphenols and are preferably 2,2',6,6'-tetrahydrocarbyl-p,p'-biphenols. According to an additional object of the invention, the tertiary alkyl-substituted biphenols may be easily dealkylated to yield the corresponding dealkylated biphenol product.
The biphenols are useful antioxidants and stabilizers in a variety of organic substances. The biphenols are also useful as components of polyester resins, for example, in the reaction with dicarboxylic acids such as terephthalic acid.
U.S. Pat. No. 3,555,052, published Jan. 12, 1971, disclosed that reduced noble metals were suitable catalysts for the oxidative coupling of phenols in the presence of oxygen to form diphenoquinones or polyarylene ethers. At column 4, line 44, it was stated that a suitable solvent for the reaction was nitrobenzene.
Prior art processes have employed oxygen or an oxygen-containing gas in order to effect the oxidative coupling reaction or alternatively an equivalent amount of a metal oxide such as silver oxide or copper oxide. These latter methods are disclosed in Blanchard, J. Org. Chem., 25, 264 (1960) and U.S. Pat. No. 4,195,189, respectively.